Stability in intimate relationships is of central concern to veterans and is crucial for their mentl health, recovery from illness, overall functioning, and quality of life. The VA is increasingly prioritizing support for intimate relationships through the promotion of recovery-based approaches that include partners and families. PTSD has a destructive effect on veteran's intimate relationships, leading to higher rates of relationship distress, problems with sexual function and intimacy, abuse, separation and divorce, and this is true for younger, as well as older, veterans. PTSD symptoms such as avoidance and numb disconnection, intrusive images and memories, and anger and irritability are incompatible with feelings of closeness and sexual intimacy. Sexuality is central to intimate relationships, self-esteem, and quality of life, yet thee are few studies of sexual dysfunction among veterans with PTSD, and none have been identified that take a biologically informed approach. Notably, the neuroendocrine processes activated in PTSD and sexual behavior are similar. The biological parallels between sexual arousal and activity and PTSD symptomatology may provide one basis for understanding problems with sexual intimacy and attachment. Sexual arousal mimics the physiological experience of fear, and once these associations have been forged it can be difficult to uncouple them. This grant builds upon a large literature on the neurochemistry and neuroendocrinology of PTSD and proposes the first in depth characterization of the problem of sexual dysfunction in veterans with PTSD. The proposed study employs a mixed-method, cross-sectional design to investigate biological and psychological correlates of sexual dysfunction in male OEF/OIF/OND combat veterans. Specifically, this investigation will assess distinct components of sexual dysfunction (e.g., lack of desire, problems with performance and consummation) and their associations with PTSD symptoms and severity and with endocrine markers, including catecholamines (epinephrine, norepinephrine, dopamine) and glucocorticoid sensitivity, that are implicated in PTSD. One hundred male OEF/OIF/OND veterans with PTSD who are currently in an intimate relationship will be studied. This study will also use qualitative interview data from 0 veterans to better characterize sexual dysfunction in PTSD. This investigation represents the first step in characterizing the psychobiology of sexual dysfunction in PTSD, and is highly clinically relevant for veterans. Understanding the psychological and biological underpinnings of PTSD related problems with intimacy and sex may help distinguish between avoidance of intimacy and inability to perform sexually, thereby directing treatment choice, contributing to the identification of clinically significant subtypes, and ultimately informing efforts to develop psychological and pharmacological interventions for sexual and relationship problems in PTSD. The information generated from this study will provide the necessary foundation for the development of a new intervention targeting sexual dysfunction in PTSD, to be pursued in a MERIT proposal by the end of the CDA period. Such an intervention has the potential to strengthen relationships and promote recovery from PTSD.